1. Field of the Invention
The present invention related to partition room and spacer ball for ball screw unit, and more particularly, to a partition room in which a spacer ball is interposed between the load carrying balls in a ball screw unit for assisting the load carrying balls to roll smoothly. Each spacer ball is confined in a specially prepared partition room and is in rotational contact with its adjacent load carrying balls at both sides, while the spacer ball is made smaller than the load carrying ball so as to increase the number of load carrying capability by smoothing the rolling of the load carrying balls.
2. Description of the Prior Art
In an ordinary ball screw unit, the mechanical operation is smoothed with reduced friction contributed by balls interposed between the bolt and nut. The structure contains a plurality of load carrying balls which being in contact with both bolt and nut, and spacer balls which being smaller than the load carrying balls are interposed between the load carrying balls. The spacer balls, which are non-load carrying are contacted load carrying balls at both sides so as to cause the two adjacent load carrying balls to rotate in the same direction thereby facilitating the ball screw unit to operate smoothly.
Meanwhile, in a ball screw unit equipped with spacer balls, if the spacer balls are made two large, the number of load carrying balls has to be reduced which results in lowering the load carrying capability of the ball screw unit, both statically and kinetically. On the other hand, if the spacer balls are made too small, the connected line of centers of successive pitch circles will be distorted to cause mutual squeezing of balls that leads to a rugged movement of the ball screw unit.
For rectifying the above shortcomings, there are some manufacturers employ a polymer partition room to separate the adjacent load carrying balls, and a spacer ball made smaller in size than the load carrying ball is confined therein to rotatably in contact with the load carrying balls at both sides. With such arrangement, the aforesaid problematic phenomenon of mutual squeezing of balls seems to have been solved. But actually, as the spacer ball is practically difficult to appropriately settle in the partition room so as to let it rotate smoothly in there, which in turn, degrades the function of the load carrying balls.
For these defects noticeable on the prior art, an improvement is seriously required.
The inventor of the present invention has plunged into this matter for years to studying and improving these defects and come up with a structure of partition room and spacer balls for ball screw unit as provided in this invention to eliminate the defects mentioned above.